The primary objective of this research program is to determine the biochemical mechanisms by which double-stranded RNA (dsRNA) (1) manifests its inhibitory effect in a broad spectrum of biological systems, and (2) regulates protein synthesis in dsRNA-sensitive cells. Previous studies have demonstrated that dsRNA influences several physiological phenomena including (a) the induction of interferon; (b) a cytotoxic effect on cultured cells; (c) a regression of solid tumors; (d) a suppression of tumor transplantation; (e) an enhancement of the immune response; and (f) the inhibition of protein synthesis in cell-free extracts. Two striking features common to these physiological mechanisms are (1) the lack of biological specificity of the dsRNA inducer, and (2) The exceptional sensitivity to physiological levels of dsRNA. The reticulocyte lysate is particularly responsive to dsRNA and provides a laboratory model for the study of several biological mechanisms induced by dsRNA. Several of these effects are similar to those observed in interferon-sensitized cells. Consequently, the lysate system is also a useful experimental model for the study of some of the events which occur during interferon induction. For example, in response to low levels of dsRNA at least two physiological activities are induced in both lysates and interferon-treated cells: (1) activation of a cAMP-independent protein kinase which regulates protein synthesis by a phosphorylation of eIF-2, the initiation factor which binds the initiator methionyl-tRNAf to the 40S ribosomal subunit; and (2) activation of an oligo A synthetase which produces the ribotrinucleotide (2',5')ApApA, which is responsible for the activation of a specific nuclease activity. The specific aims of this research project are to utilize the lysate system to (a) isolate and define the molecular components involved in the functions described above; (b) to monitor similar functions in cultured cells before and after exposure to various types of environmental or physiological stress; and (c) to examine these functions in developing cells such as erythroleukemia cells which undergo differentiation in response to a variety of stimuli.